1. Field of the Invention
This invention relates generally to the kinematic arrangement of an automatic transmission, and, more particularly to stabilizing a planetary pinion carrier using a preload.
2. Description of the Prior Art
In a planetary gear unit of the type used in automatic transmissions for motor vehicles planetary pinions are supported for rotation on a carrier comprising discs that are spaced axially to provide space for the pinions. The carrier is usually piloted into its correct position in the assembly on pilot surfaces formed in adjacent components.
For example, one of the carrier discs may be piloted into position on a spline and the other disc on the race of a one-way clutch (OWC). The race may not be perfectly round, and the spline may not be perfectly centered on the clutch race.
These features produce an inherent imbalance in the carrier, causing the carrier to tip on its spline and generate a large force that causes the carrier to track the out-of-round clutch race. When the carrier is piloted on imperfect interfaces, large impact loads are generated when the carrier is forced back to a centerline by the outer race profile. These impact loads on the carrier tend to upset the rocker element of the OWC, causing the rocker to pivot toward engagement when it should retract to an over-running position. When the carrier is impacted by the outer race, actuating springs, which urge the rocker toward engagement, can be destroyed and the clutch's function lost.
A need exits in the industry for a technique that avoids over-constraining the gearset and maintaining the carrier aligned with the centerline during no torque, coast events.